The earliest weeks of human life may represent the most consequential period of brain organization ever studied — and until now, no comprehensive synthesis existed to map what is actually happening inside a newborn's resting brain. A new systematic review covering 103 studies changes that, offering the most consolidated picture yet of how neural networks self-organize before formal learning even begins.
The review, published in Neuroscience and Biobehavioral Reviews, synthesized task-free functional connectivity (FC) research spanning the first 100 days post-partum. Across this literature, neonatal brains consistently displayed small-world network topology — a structural arrangement characterized by dense local clustering alongside emerging long-range connections, a configuration associated with efficient information transfer in mature brains. Sensorimotor, visual, and auditory networks emerged as robust, highly interconnected hubs early on, their architecture supported by local myelination patterns and subcortical scaffolding. Higher-order networks, including the default mode, frontoparietal, and salience networks, were identifiable but notably less segregated, consistent with their dependence on structural pathways still undergoing development. The review also documented a progressive strengthening of interhemispheric connectivity and increasing modularity across the 100-day window, alongside substantial interindividual variability shaped by both biological and environmental factors.
This synthesis carries meaningful implications for developmental neuroscience and, eventually, clinical pediatrics. The finding that higher-order networks exist but remain poorly differentiated at birth directly challenges any assumption that these systems are blank slates; instead, they appear to be early drafts awaiting experience-dependent refinement. The authors frame this through Interactive Specialization theory, proposing that resting-state FC acts as a form of intrinsic pre-training — the brain rehearsing network configurations before external stimuli drive specialization. The primary limitation of this review is the heterogeneity inherent across 103 independent studies, including variation in imaging protocols and gestational age ranges. Still, the breadth of coverage makes this an incrementally important, field-anchoring contribution rather than a paradigm-shifting one.